The purpose of this study is to compare same-day discharge rates and recovery outcomes across an adult patient population undergoing elective Total Knee Arthroplasty (TKA), and randomized to receive either spinal block anesthesia or Total IntraVenous Anesthesia (TIVA).

Primary Aim: assess same-day discharge rates between study arms (TIVA vs spinal).

Secondary Aim: Postoperative comparison of recovery during PostOperative Anesthesia Care Unit (PACU) admission, diagnostic assessment scores; outcomes related to cognition, hemodynamic stability, pain, nausea and vomiting; analysis of IntraOperative electroencephalogram (EEG) monitoring metrics, e.g., total suppression time, average Bi-spectral Index monitor (BIS) value, Spectral Edge Frequency (SEF); ability for Physical Therapy (PT) evaluation prior to discharge; longterm-followup (LTFU), hospital readmission, return to surgery, etc.; adverse event (AE) monitoring.

Same-day discharge after total knee arthroplasty (TKA) has become a central goal within Enhanced Recovery After Surgery (ERAS) protocols, particularly in large academic centers. Spinal anesthesia is widely used in this setting and offers advantages through avoidance of general anesthesia-related risks, including airway instrumentation and systemic anesthetic exposure; however, spinal anesthesia may also be associated with prolonged motor blockade, urinary retention, and delayed mobilization, which can hinder same-day discharge in some patients. Rare risks include headache (sometimes called a spinal headache), back soreness, the numbness spreading too high, or the spinal not working well enough and needing conversion to general anesthesia. Very rare but serious risks include infection, bleeding around the spinal cord, or nerve injury.

Total intravenous anesthesia (TIVA) represents an alternative approach that avoids neuraxial anesthesia and its associated risks, including motor weakness and urinary retention, and may reduce postoperative nausea and vomiting. However, TIVA typically requires airway instrumentation and exposure to general anesthetic agents, which carry risks such as sore throat, airway-related discomfort, dental trauma, and potential concerns regarding anesthetic dosing and recovery, particularly in older adults. Processed EEG-guided anesthesia has been proposed as a strategy to optimize anesthetic depth during general anesthesia and potentially reduce overdosing, though its impact on recovery outcomes within contemporary ERAS pathways remains incompletely defined.

This research will address this knowledge gap through a prospective, randomized trial. By comparing same-day discharge rates as the primary outcome-and examining recovery efficiency, postoperative complications, cognitive outcomes, and patient satisfaction as secondary and exploratory measures-this study will provide foundational evidence to inform anesthetic selection. Ultimately, these findings have the potential to refine perioperative care, optimize recovery, and inform future definitive trials and clinical practice guidelines for TKA, improving outcomes for a growing elderly surgical population.

A study comparison of the two anesthesia techniques (TIVA vs spinal-block) in patients undergoing total knee arthroplasty (TKA) is appropriate because anesthetic choice directly influences perioperative recovery, same-day discharge rates, and patient-centered outcomes. Total Knee Arthroplasty (TKA) represents one of the most common and rapidly increasing elective procedures worldwide, particularly among the elderly population at higher risk for adverse outcomes and longer postoperative recovery. A prospective, randomized study design allows for a controlled comparison of the two widely utilized anesthetic techniques within the context of modern ERAS protocols, while also incorporating standardized follow-up to capture both short-term and 90-day long-term outcomes. Beyond individual patient recovery, this research carries broader public health implications: with an aging population and rising demand for TKA, optimizing perioperative pathways that enhance recovery, reduce complications, and support same-day discharge has the potential to decrease healthcare utilization, lower costs, and improve the sustainability of orthopedic care delivery.

Based on our experience caring of these patients over the years, patients with strong preferences or contradictions to one of the two approaches are relatively small (~10-15%). Most patients defer to their anesthesiologists and surgeons to provide the best care plan for them. In the current practice, both anesthesia approaches are widely acceptable care for most patients undergoing TKA and no clear advantages in risk/benefit ratio in same day discharge between methods of anesthesia.

This is a single-center, prospective, randomized clinical trial. Study enrollment will consist of approximately 150-patients set to undergo elective total joint arthroplasty (TKA), at the University of Chicago Medicine (UCM); with 66-evaluable participants randomly assigned to each study arm (TIVA vs Spinal-block). Most TKA-patients are evaluated at least 1-week prior to their surgery by a member of the anesthesia team in the Anesthesia Pre-Operative Clinic (APMC) in preparation for the anesthetic plan to be administered. Eligible patients must meet initial study criteria regarding 'type of surgery' (TKA) and 'discharge plan' (same-day) to be approached regarding their interest in study participation. Potential patients will be contacted on the day of their preoperative evaluation in APMC or via phone following, by a member of the research team with experience consenting patients. Interested patients will:

• have plain language used to describe study details,
• be given time consider the informed consent material and ask questions,
• affirm their understanding of study details,
• be able to consent for themselves.

Patients showing interest by phone will be approached again on the day of surgery in the UCM-preoperative area, where the informed consent form (paper) can be signed, and baseline study diagnostic assessments can be captured. Only after consent and enrollment is confirmed can a patient be randomized to a study arm (TIVA vs spinal block).

Active study participation can last up to 7-days, following surgery, that includes survey assessment interviews to determine postoperative recovery status; with an additional long-term follow-up (LTFU) planned at day-90 via electronic medical record (EMR). Assessments to determine cognitive and physical function will be conducted at specific timepoints via investigator initiated interview (in-person and phone), using validated diagnostic surveys. Patient response will dictate length of time to complete.

Diagnostic Survey Assessments:

• Short Portable Mental Status Questionnaire (SPMSQ)
• 3-Minute Diagnostic Confusion Assessment Method (3D-CAM)
• Numeric Pain Rating Scale (NPRS)
• Numeric Rating Scale (NRS)

Diagnostic Survey Assessment Schedule

Preoperative Baseline (BL):

• SPMSQ (in-person, 3-minutes)
• 3D-CAM (3-minute)

PostOperative (Day-0):

• SPMSQ (in-person, 3-minutes)
• 3D-CAM (in-person, 3-minutes)
• NPRS (in-person, 1-minute)
• NRS (in-person, 1-minute)

PostOperative Day-1 (POD1):

• SPMSQ (via phone, 3-minutes)
• 3D-CAM (via phone, 3-minutes)
• NPRS (via phone, 1-minute)
• NRS (via phone, 1-minute)

An 'abnormal' 3D-CAM score in PACU will trigger additional assessment survey completion

PostOperative Day-3 (POD3):

• SPMSQ (via phone, 3-minutes)
• 3D-CAM (via phone, 3-minutes)

PostOperative Day-7 (POD7):

• SPMSQ (via phone, 3-minutes)
• 3D-CAM (via phone, 3-minutes)

Active participation will conclude either after, POD1 or POD7 (if triggered). Longterm-Followup (LTFU) will be conducted at PostOperative Day-90 (POD90) via electronic medical record (EMR).

Inclusion Criteria:

• Adults aged ≥18 years.
• Scheduled to undergo elective primary total knee arthroplasty (TKA) or robotic total knee arthroplasty (TKA) at the University of Chicago.
• Eligible for same-day discharge (SDD) based on established orthopedic and anesthesia criteria.
• Able to provide written informed consent.
• The ability to comprehend and complete cognitive assessment surveys and questionnaires.
• Consent to receive either Total IntraVenous Anesthesia (TIVA) or Spinal-block Anesthesia in a randomized manner
• No contraindication to either TIVA or spinal anesthesia

Exclusion Criteria:

• Age <18 years.
• Patients undergoing revision TKA or procedures other than elective primary TKA.
• Ineligibility for same-day discharge as determined by the surgical or anesthesia team.
• Contraindications to either anesthetic technique (e.g., spinal block anesthesia contraindicated due to coagulopathy, infection at puncture site, or patient refusal).
• Known allergy or hypersensitivity to study-related medications.
• Significant pre-existing cognitive impairment or dementia that would preclude valid participation in Short Portable Mental Status Questionnaire (SPMSQ), and 3-Minute Diagnostic Assessment for Confusion Assessment Method (3D-CAM) assessments.
• Severe chronic pain syndromes (e.g., fibromyalgia, centrally mediated pain disorders) that could confound perioperative pain assessment.
• Body mass index (BMI) > 40.
• Prisoners or other vulnerable populations unable to provide voluntary consent.
• Unable to give appropriate consent or difficult to comprehend and complete cognitive assessment surveys and questionnaires

Per institutional regulation, and at the discretion of Principal Investigator, de-identified data may be shared with researcher(s) at the University of Chicago.

De-identified data may be shared adhoc at the discretion of the principal investigator, following completion of study enrollment and data analysis.

Only researchers and statisticians at the University of Chicago may have access to any shared de-identified study data.